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Vogel-Tammann-Fulcher

Unfortunately, reliable experimental estimates of the configurational entropy are unavailable to enable explicit application of the AG model for polymer fluids. Instead, the temperature dependence of t in polymer melts is often analyzed in terms of the empirical Vogel-Fulcher-Tammann-Hesse (VFTH) equation [103],... [Pg.153]

Most viscosity-temperature relationships for glasses take the form of an Arrhenius expression, as was the case for binary metal alloys. The Vogel-Fulcher-Tammann (VFT) equation is one such relationship. [Pg.293]

A Vogel-Fulcher-Tammann-Hesse equation can be used to characterize the temperature dependence of the relaxation times for these six different degrees of cure, 0.70, 0.75, 0.80, 0.825, 0.90, and 0.95 ... [Pg.143]

The relaxation kinetics of the Arrhenius and Eyring types were found for an extremely wide class of systems in different aggregative states [7,52-54]. Nevertheless, in many cases, these laws cannot explain the experimentally observed temperature dependences of relaxation rates. Thus, to describe the relaxation kinetics, especially for amorphous and glass-forming substances [55-59], many authors have used the Vogel-Fulcher-Tammann (VFT) law ... [Pg.13]

Vogel-Fulcher-Tammann (VFT) equation [24] in the modified form ... [Pg.10]

Inserting Eq. (4-16) into Eq. (4-10) gives the Vogel-Fulcher-Tammann-Hesse equation, where now the Vogel temperature To = U/A.2R can be computed from the energy U between trans and gauche states. The values of U obtained indirectly in this way, using... [Pg.204]

It appears, however, that the mode-coupling theory is not able to explain some of the most significant slow-relaxation processes of these more complex glass formers. In particular, it cannot explain the success of the Vogel-Fulcher-Tammann-Hesse (VFTH) equation for the temperature-dependence of the relaxation time near the glass transition. The mode-coupling theory predicts instead a power-law dependence of the longest relaxation... [Pg.216]

CONSISTENCY OF THE VOGEL - FULCHER - TAMMANN (VFT) EQUATIONS FOR THE TEMPERATURE-, PRESSURE-, VOLUME-AND DENSITY- RELATED EVOLUTIONS OF DYNAMIC PROPERTIES IN SUPERCOOLED AND SUPERPRESSED GLASS FORMING LIQUIDS/SYSTEMS... [Pg.93]

Keywords glass transition, dynamics, Vogel-Fulcher-Tammann counterparts, negative pressures, fragility... [Pg.93]

Trachenko, K. (2008) The Vogel-Fulcher-Tammann law in the elastic theory of glass transition J. Non-Cryst. Solids 354, 3903-3906. [Pg.104]

In order to determine the structural relaxation times for the octa-O-acetyl-lactose we analyzed dielectric loss spectra of this carbohydrate with use of the Havriliak- Negami function. The temperature dependence of logioTa was fitted to the Vogel- Fulcher- Tammann (VFT) function... [Pg.371]

E0 and the infinite temperature relaxation time To are independent of temperature, and (ii) in the isotropic phase near the I-N transition, the temperature dependence of ts2(T) shows marked deviation from Arrhenius behavior and can be well-described by the Vogel-Fulcher-Tammann (VFT) equation ts2(T) = TyFrQxp[B/(T — TVFF), where tvff, B, and tvft are constants, independent of temperature. Again these features bear remarkable similarity with... [Pg.295]

In polymers, the glass transition phenomenon has been related to the dielectric a-relaxation processes through the Vogel-Fulcher-Tammann (VET) equation [9], and it can be characterized by means of their molecular dynamics analysis. [Pg.16]

In the a-process, the viscosity and consequently the relaxation time increase drastically as the temperature decreases. Thus, molecular dynamics is characterized by a wide distribution of relaxation times. A strong temperature dependence presenting departure from linearity or non-Arrhenius thermal activation is present, owing to the abrupt increase in relaxation time with the temperature decrease, thus developing a curvature near T. This dependence can be well described by the Vogel-Fulcher-Tammann-Hesse (VFTH) equation [40, 41], given by Equation 2.1 ... [Pg.17]

See other pages where Vogel-Tammann-Fulcher is mentioned: [Pg.101]    [Pg.102]    [Pg.90]    [Pg.91]    [Pg.140]    [Pg.160]    [Pg.90]    [Pg.91]    [Pg.101]    [Pg.47]    [Pg.169]    [Pg.196]    [Pg.194]    [Pg.324]    [Pg.455]    [Pg.472]    [Pg.499]    [Pg.518]    [Pg.211]    [Pg.10]    [Pg.94]    [Pg.142]    [Pg.262]    [Pg.288]    [Pg.42]   


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